1. Field of the Invention
The invention relates to a device for driving a drilling and/or impacting tool comprising a shaft, which is arranged, if necessary, in a rotatable manner in a housing, and one end of which is adapted to be fastened to the tool, whereas the other end is accessible to an oscillating impact body which is movable by means of a guide in the housing, whilst a rotatable driving shaft through a transmission can be set for moving the tool shaft and/or the impact body.
2. Description of Background Art
A device of the kind set forth in the preamble, also known by the term of rotohammer, impact drilling machine or hammer drilling machine is in general provided with an impact body arranged in a cylindrical guide. The impact body is freely reciprocatable as a piston in the cylinder, and the drive is performed by a main piston arranged at the bottom of the cylinder and being driven by a motor in an oscillatory manner. As a result of the pressure differences between the two pistons a free impact effect is produced on the one hand on the tool shaft, whereas on the other hand impact contact between the main piston and impact body is avoided by the air cushion, which may be regarded as being a progressively operating air spring. Therefore, this spring represents the reversal of the direction of movement.
Such devices are, however, fairly complicated in construction and due to the freedom of movement of the impact body the required impact frequency cannot be attained at all numbers of revolution. Moreover, due to the adiabatic compression in the cylinder cinetic energy loss occurs apart from friction loss due to the required seals, which becomes manifest in heat and wear.